Digital images are typically processed prior to displaying or otherwise using the images in various applications. Image processing is a form of signal processing in which the input is an image, such as a photograph or frame of view and the output is an image or parameters related to the image, which may then be used in various applications, such as computer vision, computer graphics etc. Image processing may be used to enhance the image, e.g., by removing noise, improving contrast or sharpness, etc., or to extract data from the image.
Computing a moving average is common in many applications including one-dimensional signal processing problems such as real-time acoustic echo cancellation. The moving average operation is typically a simple rectangular or boxcar filtering that is performed by adding newer samples coming into one end of the window, and subtracting older samples leaving from the other end at a step size required by the resolution of the moving average computation. The two-dimensional (2D) equivalent is typically performed by taking 2D differential among four corners of the intended spatial area, e.g., if rectangular, in an integral image. Variations of integral image exist to support rotation and non-rectangular areas when necessary. For sophistication beyond uniform 2D filters, multiple integral images can be stacked to mimic a desired filter shape with the trade-off between the cost of computational complexity and metrics such as the accuracy of filter approximation or other depending on the application. For some of the filter shapes, such as a Gaussian function, a more effective approximation is possible by repeated boxcar filtering, using integral images for computational efficiency, commonly referred to as repeated integral images method.
However, despite its accuracy, the cost of the data I/O bandwidth that results from the conventional architecture of repeated integral images method sometimes render the method unsuitable for many applications. Thus, an improved architecture for repeated integral images is desired.